Such a fixed base station is described in the book "The GSM-System for Mobile Communications" by M. Mouly and M.-B. Pautet, which was published in 1992 by the publishing firm at 49, rue Louise Brunea, F-91120 Palaiseau, France. It describes a fixed base station for the GSM cellular radio network (Global System for Mobile Communications), which exchanges radio pulses with mobile stations within a radio cell in accordance with the TDMA (Time Division Multiple Access) radio transmission process. Chapter 6.1.5.2 "Timing Advance" describes how the propagation times of the TDMA radio pulses are balanced inside the cell, whereby a so-called "Timing Advance" is taken into consideration when these radio pulses are transmitted by the mobile station. This is the time interval at which the TDMA radio pulses are transmitted by the mobile station in advance of the time slot sequence within the fixed base station. The timing advance can be changed between 0 .mu.s and 233 .mu.s, which serves to compensate for signal propagation times of the same size within the radio cell. The expansion of the radio cell is limited to a maximum radius of 35 km, which corresponds to the maximum signal propagation time of 233 .mu.s. In the described GSM radio network, the limitation of the radio cell is based on a limitation of the time advance coding. Radio pulses from mobile stations outside of this radio cell cannot be received. To achieve a desired enlargement of the radio cell, the book proposes to charge only every other time slot within the time slot sequence, which is the same as enlarging the protection times between radio pulses. However, this measure requires a change in the fixed base station's receiving method, as indicated by the authors themselves on page 347. Furthermore, this measure leads to the fact that only half of the channel capacity can be used for a radio transmission. Measures to circumvent these problems are not addressed in the book.
The Australian patent application PM 2427 of Nov. 15, 1993 proposes to equip the TDMA fixed base station with two receivers receiving on one frequency, but time-displaced with respect to each other by the maximum signal propagation time. This causes one of the receivers to receive the TDMA radio pulses from mobile stations inside the radio cell, and the other receives TDMA radio pulses from mobile stations outside of the radio cell. In this way the supply area of the TDMA fixed base station becomes an extended radio cell with double the cell radius. However, the TDMA radio pulses that are transmitted by the mobile stations can collide with each other at the receiving place, i.e. the location of the fixed base station. This creates interference between the TDMA radio channels.